Method and apparatus for supporting a turf mower cutting unit

Abstract

One aspect of the invention relates to a cutting unit joint (22) which can be located between a lift arm (18) and a cutting unit (20). Cutting unit joint (22) includes a four-bar linkage preferably including pairs of pivoting links (46 and 48) which create a "virtual pull point" at any desired location. With regard to one embodiment, a cutting unit (20), the virtual pull point is even located below ground, when the cutting unit (20) is generally level. This configuration reduces or eliminates cutting unit "bobbing." In another embodiment, in connection with a cutting unit (20'), the virtual pull point is located roughly at the centerline of the reel, to maintain a good "seal" between the cutting unit (20') and a lift arm supported grass basket (52'). Another aspect of the present invention relates to a self-contained damper (76) connected to lift arm (18), the damper (76) resisting upward movement at a velocity or frequency consistent with cutting unit "bobbing."

We claim: 
     
       1. A turf maintenance machine comprising: (a) a traction vehicle;   (b) a reel-type cutting unit; and   (c) means including a four-bar linkage for connecting the cutting unit to the traction vehicle, wherein the connecting means comprises: i. a lift arm;   ii. a pivot joint connecting the lift arm to the traction vehicle; and   iii. a cutting unit joint connecting the cutting unit to the lift arm, wherein the four-bar linkage is a component of the cutting unit joint.     
     
     
       2. The turf maintenance machine of claim 1, wherein the pivot joint comprises a self-contained damper which prevents sudden upward movement of the lift arm consistent with cutting unit bobbing. 
     
     
       3. The turf maintenance machine of claim 1, wherein a virtual pull point is established by the four-bar linkage and the virtual pull point is below ground, when the cutting unit is on generally level ground, whereby cutting unit bobbing is substantially eliminated. 
     
     
       4. The turf maintenance machine of claim 1, wherein (i) the cutting unit is a reel-type cutting unit having a rotatable reel with a reel centerline; (ii) a virtual pull point is established by the four-bar linkage; and (iii) the virtual pull point is located proximate the reel centerline. 
     
     
       5. The turf maintenance machine of claim 1, wherein the cutting unit is a reel-type cutting unit having a rotatable reel with a reel centerline, and wherein the turf maintenance machine further comprises a grass basket supported by the lift arm, wherein a virtual pull point is established by the four-bar linkage and the virtual pull point is located proximate the centerline of the reel, whereby the grass basket and the cutting unit are maintained in close proximity even as the cutting unit follows the contour of the turf. 
     
     
       6. A turf maintenance machine comprising: (a) a traction vehicle;   (b) a reel-type cutting unit; and   (c) a cutting unit support system connecting the cutting unit to the traction vehicle, the support system comprising a four-bar linkage, wherein: i. a first bar of the four-bar linkage is rigidly connected to the cutting unit;   ii. the cutting unit support system comprises a lift arm, and a second bar of the four-bar linkage is rigidly connected to the lift arm;   iii. the lift arm carries a cutting unit carrier frame and attached to the carrier frame is a forward link and a rearward link;   iv. the links are pivotally connected to the carrier frame and the cutting unit; and   v. the forward link forms a third bar of the four-bar linkage, and the rearward link forms a fourth bar of the four-bar linkage.     
     
     
       7. The turf maintenance machine of claim 6, wherein the cutting unit is supported by a roller, and a virtual pull point is established at the point of intersection of imaginary lines passing through the links, wherein the virtual pull point is roughly located at the same height or below the cutting unit support roller. 
     
     
       8. The turf maintenance machine of claim 6, wherein a virtual pull point is established at the point of intersection of imaginary lines which pass through the links and the cutting unit comprises a cutting reel having a reel centerline, and wherein the virtual pull point is located proximate the reel centerline. 
     
     
       9. The turf maintenance machine of claim 6, wherein a virtual pull point is established by the four-bar linkage and the virtual pull point is below ground, when the cutting unit is on generally level ground, whereby cutting unit bobbing is substantially eliminated. 
     
     
       10. The turf maintenance machine of claim 6, wherein (i) a virtual pull point is established by the four-bar linkage; (ii) the cutting unit is supported by front and rear rollers; and (iii) the virtual pull point is proximate the rear roller when the cutting unit is ascending and proximate the front roller when the cutting unit is descending, whereby ground following is enhanced.